The present invention relates to a side airbag apparatus structured such as to inflate and deploy an airbag between a body side portion and a seat for a vehicle in the case that an impact is applied to the vehicle from a side direction, and to reduce the impact by the airbag so as to protect an occupant.
A side airbag apparatus is widely known as an apparatus for protecting an occupant from impact applied from a side of a vehicle, such as in the case of side collision. The side airbag apparatus includes an inflator and an airbag or the like. The airbag is stored in a seat back (a backrest portion) of the seat for the vehicle in a state of being folded so as to be made compact.
In the side airbag apparatus, when an impact is applied from the side of a body side portion of a vehicle, the inflator discharges gas into the airbag. The airbag is inflated and deployed by the gas and shoots forward out of the seat back in a state of leaving a part of the airbag within the seat back. The airbag is then inflated and deployed forward from the backrest in a narrow space between the occupant seated in the vehicle seat and the body side portion. The inflated and deployed airbag is interposed between the occupant and the body side portion making an intrusion into a passenger compartment so as to restrain the occupant. The gas within the airbag is thereafter discharged to the outside of the airbag through a vent hole provided in the airbag. The impact transmitted to the occupant from the side direction through the body side portion is reduced on the basis of the inflation and deployment of the airbag and the reduction of the internal pressure of the airbag caused by discharge of the gas.
In many cases, the vent hole is provided in a vehicle outer side or a vehicle inner side in the airbag in a state of being deployed without being filled with the gas. In addition, there have been proposed a side airbag apparatus in which a vent hole is provided in a front end of an airbag as disclosed in Japanese Laid-Open Patent Publication No. 8-225054, a side airbag apparatus in which a vent hole is provided in a vehicle seat as disclosed in Japanese Laid-Open Patent Publication No. 2001-114065.
In accordance with any one of the side airbag apparatuses mentioned above, the vent hole is provided in a section which is away from a gas outlet of an inflator for delaying a discharge timing of the gas from the airbag. However, in the apparatus disclosed in each of the publications, only the position of the vent hole is contrived. Accordingly, there is a risk that that the gas is unnecessarily discharged through the vent hole from a starting time of the inflation of the airbag. Therefore, the amount of the gas fed to the airbag from the inflator is reduced at an amount of the gas discharged at the starting time of the inflation of the airbag. Accordingly, an ascent of an internal pressure of the airbag is deadened and the speed of inflating and deploying the airbag becomes slower.